Transition metal oxides and mixed oxides are the largest group of materials for photocatalytic applications. Many highly active compounds are known from literature for environmental remediation, pollutant degradation and solar fuel generation. However, most of these oxides can only absorb UV light to perform photocatalytic reactions at their surface due to their large band gap. In this review, we present the recent progress in non-metal doping of transition metal oxides and mixed oxides, one of the major strategies to reduce the large band gap of semiconductor materials into the visible light range. We outline the advantages of this strategy compared to other band gap engineering methods, and especially stress the effect of efficient homogeneous non-metal doping on the optical, electronic and photocatalytic properties of photocatalysts, compared to surface doping and surface modification, including the effects of an open crystal structure on the efficiency of the doping process. We then present the highlights and breakthroughs of the last ten years in the research field and point out major improvements important for future applications, covering all the available non-metal doped transition metal oxides concerning photocatalytic reactions. (C) 2013 Elsevier B.V. All rights reserved.